A team of assessors says Iran violated a United Nations arms embargo by directly or indirectly providing missiles and drones to Yemen's Houthi rebels.
The team travelled to Saudi Arabia in November and December of last year and examined remnants of missiles fired by the Houthis in those months, as well as in May and July.
The report, excerpts of which were obtained by news agencies and diplomats on Friday, said: "The panel has identified missile remnants related to military equipment and military unmanned aerial vehicles that are of Iranian origin and were introduced into Yemen after the imposition of the targeted arms embargo" in 2015.
Referring to the UN Security Council resolution that imposed the embargo, it said: "As a result, the panel finds that the Islamic Republic of Iran is in non-compliance with paragraph 14 of Resolution 2216 in that it failed to take the necessary measures to prevent the direct or indirect supply, sale or transfer of missile and unmanned aerial vehicles to the Houthi-Saleh alliance."
Iran denies supplying the rebels with arms.
During a security council meeting on December 19, US ambassador Nikki Haley called the Houthis' firing of a ballistic missile earlier that day "a flashing red siren" and said the United States would push for action against Iran, but Russia signalled its opposition.
That missile attack had been aimed at a meeting of Saudi leaders in the capital, Riyadh, but was intercepted by the kingdom's air defences.
A Saudi-led military coalition is fighting the Houthis in Yemen on behalf of the internationally recognised government of president Abdrabu Mansur Hadi.
On Friday, a coalition air strike in the western coastal province of Hodeidah killed six senior Houthi commanders including Yehya Hussein Al Ayani, a close aide of Houthi leader Abdulmalik Al Houthi.
Twenty other Houthi fighters were killed in a battle further north along the coast on Friday when Yemeni troops repelled an attempt to break a siege of rebel pockets around the city of Midi in Hajja province, the army's 5th military zone said on its Facebook page.
Yemeni military spokesman Col Nasser Al Rydhami told The National that Al Ayani and the other commanders were killed in Al Khoukha district, where pro-government forces are pressing an offensive towards the rebel-held port of Hodeidah after seizing the area late last year.
Al Ayani was in the Houthi party that killed former president Ali Abdullah Saleh on December 4 after storming his residence in Sanaa. He also served in the rebels' rapid reaction force as well as on the northern border with Saudi Arabia, according to the Al Arabiya news channel.
The Houthis killed Saleh after he broke off his alliance with them and called for talks with the Saudi-led coalition to end the war. They then launched a crackdown on his supporters that has seen hundreds killed or arrested.
On Saturday, several women were injured when Houthi security forces broke up protest against the crackdown and looting by the rebels in the capital.
The women had gathered Al Tahreer square holding banners and chanting slogans against the rebels, as well as demanding that they hand over Saleh's body. The rebels reportedly buried the former president in his hometown days after killing, with fewer than 20 people present.
The demonstrators were attacked by the Houthi women's police, known as Al Zaynabyat, with several being arrested and taken to Al Gudairi police station in the old city and others taken to hospital for treatment, a source in Sanaa told The National.